1. Field of the Invention
The present invention relates to a dye recording method for recording a half-tone image with dyeing by heating selectively the ink supplied to the surface of a recording medium, a dye recording apparatus therefor, a recording ink for the dye recording method and a thermal head used for the dye recording apparatus.
2. Prior Art
Recently, thermal transfer recording of the sublimation type has attracted attention because excellent gradation recording can be realized and a full-color image can be recorded. In the method, an ink sheet having an ink layer including a sublimation dye is provided, and the dye is transferred by thermal printing from the rear side of the ink sheet to a recording medium having a dyed layer which can receive the sublimed dye.
In a thermal transfer recording apparatus for performing the thermal transfer recording (refer for example IEEE Transaction on Consumer Electronics, Vol. CE-28, No. 3, pp. 226-231, August 1982), a recording medium having the dyed layer is supported on a platen, while an ink sheet having the ink layer supported on a sheet-like substrate is supplied between a platen and a thermal head and the ink layer is pressed to the dyed layer. The dyed layer includes a dye which can sublime. Then, heating elements in the thermal head are heated selectively according to image signal and the dye included in the ink layer is transferred to the dyed layer. The transferred dye forms a transferred ink image.
However, in such dye recording, when the dye is transferred thermally, the air included between the ink sheet and the head, the sheet-like substrate and the ink layer must also be heated. Especially, the sheet-like substrate has to be heated at a temperature above that of the dye in order to heat from the rear side of the ink sheet. Therefore, a large amount of power is needed for dye recording.
Further, because the ink extracted from an ink sheet by heating is hard to be supplemented, the ink sheet is discarded. Therefore, the running cost is high and the resources cannot be used effectively.